Atomic superconductor one-ups squid

PORTLAND, Ore.—Circulating ultra-cold atoms around a ring exhibits superfluidity—the atomic version of superconductivity—potentially enabling sensors capable of tracking rotational motion in gyroscopes of unparalleled accuracy, according to the National Institute of Standards and Technology and Technology (NIST).

When gases are cooled to near absolute zero, they condense into a superfluid that can be launched around a ring to exhibit perpetual motion, similar to the manner in which superconducting quantum interference devices (squids) detectors circulate electrons around a superconducting ring. Such atomic Squids could enable ultra-precise gyroscopes the size of micro-electro-mechanical systems.

NIST researchers cooperated with the University of Maryland on the world's first atom-circuit formed by a loop of atoms in a superfluidic state which can be switched on and off with a laser controlled barrier. The research team was able to demonstrate perpetual motion—called persistent current—for a record-setting 40 seconds.

NIST said it was working toward a future atomtronics era where all circuit components would be based on atomic-scale mechanisms that can harness quantum effects to create superconductors, superinsulators and now superfluidic devices.

Atomic-scale circuit harnesses ring of ultracold sodium gas (red) circulating around a ring, with a laser-based barrier stopping the flow of atoms around the circuit (left); without the barrier the atoms circulate around the ring (right).

Colin - a question. Once the flow is stopped by the laser, what starts it again? It is not clear whether or not the flow needs restarting from an external source, e.g. electric field or what? What am I missing?